This application relates to a gas turbine engine, wherein a variable volume of cooling air is passed over a heat exchanger.
Gas turbine engines are known and, typically, include a fan delivering air into a bypass duct as propulsion air. The air is also delivered into a core engine where it passes into a compressor. Compressed air is then moved into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
There are a number of fluids within a gas turbine engine. As an example, there is hot air in the engine, adjacent the combustor and downstream of a combustor. The prior art has provided ways of cooling this hot air, such as a heat exchanger that receives a flow of cooling air.
In addition, fuel and oil, as utilized on the gas turbine engine, may also pass to a heat exchanger where it is cooled by cooling air.
It was typically true that the cooling air was passed over these heat exchangers at all periods of operation of the associated gas turbine engine. This was somewhat inefficient, in that, the heat exchanger does not constantly need cooling.
More recently, it has been proposed to have a door which may move between open and closed positions to either block or allow flow of the cooling air across the heat exchanger. This reduces the volume air which is utilized as cooling air at times when little or no cooling air is required.
Overall, this will increase the efficiency of the associated gas turbine engine.